As you navigate your way through this site, you' ll run across a number of terms that are specific to the cement and concrete industry.
Aggregates typically make up about 60%-75% concrete volume are usually termed coarse aggregate (gravels and crushed stones larger than 5mm in size) and fine aggregate (sands either natural or manufactured with particle sizes 5mm or less in size).
Air Content is the total volume of air voids, both entrained and entrapped, in cement paste, mortar or concrete.
Air Entrainment is the intentional introduction of air in the form of minute, disconnected bubbles (smaller than 1 mm) during mixing of concrete, mortar, plaster or grout to improve desired characteristics such as cohesion, workability and durability.
Air - Entrapped - occurs naturally (unintentionally) in most concrete mixes as a result of mixing action and typically makes up 1-2% of the volume of the concrete.
Bleeding is the flow of mixing water from a newly placed concrete mixture toward the concrete surface caused by the settlement of the denser solid materials in the mixture.
Cement & Cementitious Materials are materials that, when combined in appropriate proportions with water, form a paste (or glue) that through a chemical reaction called hydration binds the aggregates (gravel, crushed stone and sands) to form concrete. These materials include, but are not limited to, Portland hydraulic cement, blended hydraulic cement,fly ash, silica fume, meta-kaolin, ground granulated blast furnace slag, calcined clay, calcined shale and rice husk ash.
Contraction (Control Joints) provide for movement in the plane of a slab or wall to induce cracking caused by drying and thermal shrinkage at preselected locations. These joints may be grooved, sawed or formed to reduce the occurrence of undesirable random cracks.
Cracking in concrete is usually associated with two basic causes; (1) stress due to applied loads and; (2) stress due to temperature or moisture changes when concrete is restrained.
Crazing are hexagonal shape crack patterns that are rarely deeper than 3 mm and are usually most evident in concrete surfaces when they're wet. They do not compromise the structural integrity of the concrete and are seldom associated with any durability issues. See Concrete Tech Tip # 3 Crazing Concrete Surfaces.
Curing is the maintenance of a satisfactory moisture content and temperature in concrete, mortar, gout, or plaster for a suitable period of time during its early stages (immediately following placing and finishing) so that the desired properties of the material can develop. Curing assures satisfactory hydration and hardening of cementing materials.
De-icing Chemicals - chemicals applied to concrete flat-work surfaces to reduce ice and snow cover. Many are chloride based and have the potential to corrode reinforcing steel or rebar, commonly incorporated in structurally reinforced concrete.
Delamination of the top 3-6 mm of concrete surfaces occurs when the surface of fresh concrete is sealed while the underlying concrete is still plastic and bleeding and still able to release air. The surface will come off, post hardening,in portions of several square centimeters to larger "sheets". See Concrete Tech Tip # 20 Delamination of Troweled Concrete
Durability is the ability of concrete, mortar, grout or plaster to resist weathering action and other conditions of service, such as chemical attack, freezing and thawing, and abrasion.
Hard-troweled/Steel Troweled/Fresno concrete surface finishes are typically applied to interior slabs to provide a tight sealed surface resistant to abrasion due to heavy traffic and compatible with subsequent floor coverings on interiors slabs such as tile, lino and carpeting. However, this method of concrete finishing should never be applied to air-entrained slabs subject to freeze-thaw exposure because hard troweling destroys the air-entrainment protection at the top surface of the slab which can lead to surface scaling as well as other forms of surface degradation or delamination.
Honeycombing is the hardened result of pour concrete consolidation in a wall, column or other concrete member. It is usually exhibited in a "honeycomb-like" feature which is immediately apparent upon form stripping. The concrete member contains segments where the aggregate has separated from the paste due to over or improper vibration and/or poorly sealed forms that have allowed the paste to escape. The extent of honeycombing of a particular concrete member along with its intended use will dictate the required level of remediation.
Hydration in concrete, mortar, grout and plaster, the chemical reaction between hydraulic cement and water in which new compounds with strength- producing properties are formed.
Mortar Flaking is the dislodging of small sections (flakes) of surface concrete, usually smaller than a dime, directly above coarse aggregate particles. It is often associated with poor curing practices, particularly under dry windy conditions. See Concrete Tech Tip #25 Mortar Flaking
Plastic Concrete is a term used typically to describe concrete in it's fresh state before it reaches its initial set point - around 3.5 MPa or 500 psi.
Plastic Shrinkage Cracking occurs when the rate of concrete bleeding is exceeded by the rate of evaporation of bleed water from the concrete surface. These fine cracks usually occur in parallel patterns and run perpendicular to wind surface direction at the time of placement. Although they may be aesthetically displeasing, they rarely compromise the durability or overall service life of the concrete. See Concrete Tech Tip #5 Plastic Shrinkage Cracking.
Scaling is the disintegration and flaking of a hardened concrete surface, frequently due to repeated freeze-thaw cycles and application of de-icing chemicals See Concrete Tech Tip # 2 Scaling Concrete Surfaces
Sealing is a process of applying a compound to an exposed concrete surface (usually following the curing period) to prevent the ingress of undesirable substances such a water and chemicals that have the potential to degrade the esthetics and durability of the finished product. Manufactures recommendations for application rates and pre-application concrete surface preparation should always be followed when applying sealing compounds to concrete.
Slump is a measure of the consistency of freshly mixed concrete, equal to the immediate subsidence of a sample of concrete moulded with a standard slump cone.
Sulphate Attack is a common form of chemical attack on concrete caused by sulphates in the groundwater or the soil manifested by expansion and disintegration of the concrete.
Water to Cementing Materials Ratio (w/c or w/cm) is the ratio by mass of the amount of water to the mass of the total amount of cementing materials in a batch of concrete or mortar stated as a decimal i.e.0.45
If you'd really like to learn a lot more about Concrete Technology perhaps you might consider enrolling in one of our classroom seminars or on-line webinars. Just look under the Education Tab of the homepage for more information about course content and registration.